Heart attacks are a common cause of death. A heart attack occurs when a portion of the heart tissue loses circulation and becomes damaged as a result (e.g., because of blockage in the heart vasculature). Heart attacks and other abnormalities can lead to ventricular fibrillation (VF), which is an abnormal heart rhythm (arrhythmia) that causes the heart to lose pumping capacity. VF occurs when normal, regular electrical impulses are replaced by irregular and rapid impulses, causing the heart muscle to stop normal contractions and to begin to quiver. Normal blood flow ceases, and organ damage or death can result in minutes if normal heart contractions are not restored. Because the victim has no perceptible warning of the impending fibrillation, death often occurs before the necessary medical assistance can arrive. Other cardiac arrhythmias can include excessively slow heart rates known as bradycardia or excessively fast heart rates known as tachycardia. Cardiac arrest can occur when a patient in which various arrhythmias of the heart, such as ventricular fibrillation, ventricular tachycardia, pulseless electrical activity (PEA), and asystole (heart stops all electrical activity) result in the heart providing insufficient levels of blood flow to the brain and other vital organs for the support of life. If such problems are not corrected quickly—typically within minutes—the rest of the body is deprived of oxygen and the person dies. Therefore, prompt care of a person experiencing ventricular fibrillation can be key to a positive outcome for such a person.
Cardiac arrest and other cardiac health ailments are a major cause of death worldwide. Various resuscitation efforts aim to maintain the body's circulatory and respiratory systems during cardiac arrest in an attempt to save the life of the patient. The sooner these resuscitation efforts begin, the better the patient's chances of survival. Implantable cardioverter/defibrillators (ICDs) or external defibrillators (such as manual defibrillators or automated external defibrillators (AEDs) have significantly improved the ability to treat these otherwise life-threatening conditions. Such devices operate by applying corrective electrical pulses directly to the patient's heart. Ventricular fibrillation or ventricular tachycardia can be treated by an implanted or external defibrillator, for example, by providing a therapeutic shock to the heart in an attempt to restore normal rhythm. To treat conditions such as bradycardia, an implanted or external pacing device can provide pacing stimuli to the patient's heart until intrinsic cardiac electrical activity returns. People who have had previous problems may be implanted with an automatic defibrillator that constantly monitors the condition of their heart and applies a shock when necessary. Other such people may be provided with a wearable defibrillator in the form of a vest such as the ZOLL® LIFEVEST® wearable cardioverter defibrillator product provided by ZOLL Medical Corporation. Other people may be treated using an external defibrillator/monitor, such as those found in a hospital or used by emergency medical services, for example, the R SERIES® or X SERIES® products from ZOLL Medical Corporation. Some people may be treated via an automated external defibrillator (AED) of the kind that is frequently seen in airports, public gymnasiums, schools, shopping areas and other public spaces. Examples of such AEDs are the AED PLUS® automated external defibrillator or the AED PRO® automated external defibrillator, both from ZOLL Medical Corporation of Chelmsford, Mass. As provided herein, the term AED refers generically to any device or system that incorporates some method or algorithm of acquiring an electrocardiographic (ECG) signal, analyzing the ECG for whether or not it is appropriate to provide a defibrillation shock to the patient(s) and which can provide a defibrillation shock.